The field of this invention relates broadly to metal fabricating. More particularly, this invention relates to the formation of thin, flat metallic strips into a twisted or generally curvilinear configuration.
The bending or twisting of a thin, elongated metallic strip into a helical shape in the past has been difficult to accomplish satisfactorily. One reason for this is that as the strip is twisted into the helical shape the strip automatically shortens in length. Normally, the strip is bound between two fixed members and as the strip is shortened in shape, the metal inherently must stretch. It does not take much twisting for the stretch achieved causes failure of the strip.
Another reason is that in the past it has been difficult to establish an even pitch of the twist. This is due to in any quality of strength throughout the strip especially due to the stretching of the strip. This results in certain portions of the strip to twist into a closer spiral than the other portions.